Late Holocene palaeovegetational and environmental changes inferred from organic geochemical proxies in sediments from Pookot Lake, southern India

The sediments from Pookot Lake situated in the Sahyadri (Western Ghats) of southern India provided a record of palaeovegetation and palaeomonsoon variations during the Late Holocene. The palaeovegetation was reconstructed using the carbon isotopic composition of bulk organic matter (δ13Corg) and organic geochemical proxies (C/N ratio, Corg %, N % and CaCO3). The vegetation composition (C3 and C4 plants) in the Pookot Lake catchment has changed in response to monsoonal variations. Around 2500 cal. years B.P., the lake had a high water level, increased aquatic plankton activity and abundant C3 vegetation in its catchment, indicating strong monsoonal conditions. From 2500 to 1000 cal. years B.P., the lake had a lower water level, decreased aquatic plankton activity and increased contribution from C4 land plants, indicating low rainfall conditions. During 1500 to 1000 cal. years B.P., the contributions from C3 land plants and aquatic plankton increased, suggesting a moderate rainfall. From 1000 cal. years B.P. to the Present, the abundances of C3 and C4 vegetation fluctuated, indicating variations in the monsoonal strength. During the Medieval Warm Period (1000 to 600 cal. years B.P.), the monsoon was strong, but it was weak during the Little Ice Age (600 to 350 cal. years B.P.). From 350 cal. years B.P. to the Present, it has been steady. A similar climatic trend is documented in other palaeovegetation records from geographically different parts of India although spatial variability exists. Archaeological lines of evidence suggest a possible climate–culture link in the region.